Oil-containing antifreezes are well known in the art. For example, ethylene glycol antifreeze compositions containing mineral oil plus an emulsifier or containing a barium sulfonate oil are well-known and were used commercially in internal combustion engine coolant systems such as those found in automobiles up until the mid-1960's. The oil in these antifreezes provided excellent corrosion inhibition for the antifreezes by coating the metal surfaces of the coolant system with a so-called "magnetic film". However, in concentrate form, these compositions are generally stable only for a very short period of time of perhaps a couple of days or less, after which time they tend to separate into two phases. Moreover, these compositions are not compatible with modern internal combustion engine coolant systems.
With the advent of antifreeze overflow-tanks used to hold the volume expansion of antifreeze in a hot engine coolant system, these rather unstable macroemulsion antifreezes were replaced with other types of antifreezes, since a macroscopic two-phase antifreeze tends to congregate the less dense oil phase in the overflow-tank and the second phase in other parts of the cooling system. For the above described reasons, macroscopic two-phase antifreezes are obsolete and current antifreezes are single phase, most notably the silicone-silicate stabilized antifreezes disclosed in U.S. Pat. Nos. 3,337,496 and 3,341,469.
More recently, homogeneous, visually single-phase antifreezes have been developed and used for internal combustion engine cooling systems from the mid-1960's to the present time, most notably the silicone-silicate stabilized antifreezes disclosed in U.S. Pat. Nos. 3,337,496 and 3,341,469. The silicate in such antifreezes provides excellent metal corrosion inhibition properties for the antifreeze.
There are disadvantages associated with each of the above two types of antifreezes. The "magnetic film" antifreezes lack the ability to remain homogeneous and single phase during storage and during use. The silicone/silicate antifreezes do not provide the oil film layer metal corrosion inhibitor that is so uniquely effective in the magnetic film type of antifreeze.